This application relates generally to rotary machines and more particularly, to an aspirating seal assembly for sealing a rotary machine.
At least some rotary machines, such as steam turbine engines, have a defined fluid flow path extending therethrough. The flow path includes, in a serial-flow relationship, a fluid inlet, a turbine, and a fluid outlet. A leakage flow path exists in some known rotary machines upstream of the primary flow path between an area of high pressure and an area of low pressure. Some rotary machines use a plurality of sealing assemblies in the leakage flow path to facilitate increasing the operating efficiency of the rotary machine. Generally, known seal assemblies are coupled between a stationary component and a rotary component to provide sealing between the high-pressure area and the low-pressure area.
In some known rotary machines, hydrodynamic face seals may be used to facilitate reducing leakage of a pressurized process fluid through a gap between the stationary component and the rotary component. Hydrodynamic face seals generally include a rotating ring and a stationary (non-rotating) ring. At the startup of at least some known rotary machines containing hydrodynamic face seals, the rotating ring and the stationary ring are biased away from each other until pressure builds up within the machine and moves the stationary ring toward the rotating ring. During operation, hydrodynamic grooves formed in the rotating ring generate a hydrodynamic force that causes the stationary ring to remain separated from the rotating ring such that a small gap exists between the two rings. However, if the high pressure acting on the stationary ring is too forceful, the hydrodynamic force created by the grooves may not be enough to keep the stationary ring from impacting the rotating ring and causing serious damage to the rotary machine.